001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.comparator;
018
019import java.io.File;
020import java.io.Serializable;
021import java.util.Comparator;
022
023import org.apache.commons.io.FileUtils;
024
025/**
026 * Compare the <b>last modified date/time</b> of two files for order
027 * (see {@link FileUtils#lastModifiedUnchecked(File)}).
028 * <p>
029 * This comparator can be used to sort lists or arrays of files
030 * by their last modified date/time.
031 * <p>
032 * Example of sorting a list of files using the
033 * {@link #LASTMODIFIED_COMPARATOR} singleton instance:
034 * <pre>
035 *       List&lt;File&gt; list = ...
036 *       ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_COMPARATOR).sort(list);
037 * </pre>
038 * <p>
039 * Example of doing a <i>reverse</i> sort of an array of files using the
040 * {@link #LASTMODIFIED_REVERSE} singleton instance:
041 * <pre>
042 *       File[] array = ...
043 *       ((AbstractFileComparator) LastModifiedFileComparator.LASTMODIFIED_REVERSE).sort(array);
044 * </pre>
045 * <p>
046 *
047 * @since 1.4
048 */
049public class LastModifiedFileComparator extends AbstractFileComparator implements Serializable {
050
051    private static final long serialVersionUID = 7372168004395734046L;
052
053    /** Last modified comparator instance. */
054    public static final Comparator<File> LASTMODIFIED_COMPARATOR = new LastModifiedFileComparator();
055
056    /** Reverse last modified comparator instance. */
057    public static final Comparator<File> LASTMODIFIED_REVERSE = new ReverseFileComparator(LASTMODIFIED_COMPARATOR);
058
059    /**
060     * Compares the last the last modified date/time of two files.
061     *
062     * @param file1 The first file to compare.
063     * @param file2 The second file to compare.
064     * @return a negative value if the first file's last modified date/time is less than the second, zero if the last
065     *         modified date/time are the same and a positive value if the first files last modified date/time is
066     *         greater than the second file.
067     */
068    @Override
069    public int compare(final File file1, final File file2) {
070        final long result = FileUtils.lastModifiedUnchecked(file1) - FileUtils.lastModifiedUnchecked(file2);
071        if (result < 0) {
072            return -1;
073        }
074        if (result > 0) {
075            return 1;
076        }
077        return 0;
078    }
079}